I still didn't watch the episode on VOOT because it simply not showing. Coming to the synopsis you have written by understanding it, Vansh is avoiding Ridhima's past - WHY? I have listed out few probabilities
1. He fell in love with her. Cannot lose her. So ignoring her past.
2. He is acting like fell in love with her and ignoring her past to gain more trust of her and play with it later
3. He wants the person behind Ridhima to come out and play the cards rather than using her as a mere pawn
4. He might have understood Ridhima is just a pawn and he started caring for her in real sense.
Above all might be the questions which everyone thought of, but if he comes to know the truth will he blame Ridhima for it? Because this poor girl came to say the truth and he using cinema lines didn't give ear to her. So what possibilities can be more?
I simply feel he is playing in his own way. Vansh ka khel has no rules. The rules are something which he creates. He is not betraying Ridhima by doing this. He is just replying to the game which KABIR has started by using Ridhima. So tomorrow, even if Ridhima feels she got betrayed by Vansh, in reality, it is not betrayal from his POV because She came to hurt him.
YES, the real betrayal is when she receives from KABIR. That is the major hit to Ridhima. Then she might feel she deserves it because she played according to Kabir tunes and got this punishment. I don't think she stupid girl will blame Vansh at that time. She will blame her stupidity and KABIR.